At present, the development of display screens tends to be narrow frame, ultra-thin, and high brightness, and the conventional backlights can't meet high grade requirements. The conventional backlight is composed of LED, multilayer films, light guide assembly, housing frame and light-shielding tape, when it is applied to meet the high grade requirements, it will cause various defects such as bright lines, light leakage, wrinkles, and glue failure, which will greatly reduce the yield of products and increase costs. Moreover, the ultra-thin, narrow frame display screen requires extremely high accuracy for cutting and assembly of the film, and the requirement for uniformity of the light output is gradually increased. Therefore, the current backlight still needs improvement.